1. Field of the Invention
The invention relates to integrated circuits, and more particularly to universal serial bus (USB) keyboard control circuitry for use in a notebook computer.
2. Description of the Related Art
Users of personal computers have been liberated from the restrictions of desktop-only use with the introduction of portable “notebook” computers. In recent years, the notebook computer has made considerable gains in both popularity and sophistication. The convenience and transportability of the notebook computer has produced a large and lucrative market for manufacturers of such machines. In general, keyboards are the primary user interface for entering information and commands into a computer. The keyboard used with a desktop computer typically contains a keyboard controller which responds to the depression of a key on the keyboard by generating a key matrix code corresponding to the depressed key, and by supplying the code in a digital form to a host or the like.
The keyboard used in a notebook computer, on the other hand, does not include the above keyboard controller. Conventionally, a special embedded controller in the notebook computer takes charge of the keyboard control function. The embedded controller is a powerful microcontroller which assumes many jobs in a notebook computer, such as power management, screen brightness adjustment, keyboard control, and so forth. However, the embedded controller is more expensive than an ordinary logic circuit and must work with the basic input/output system (BIOS). Furthermore, manufacturers must pay a royalty to obtain the rights to make and sell notebook computers using the keyboard BIOS. In addition to the royalty expense, the manufacturer is required to design a program cooperating with the licensed keyboard BIOS to enable the embedded controller to carry out the keyboard control function. Unfortunately, this program must be rewritten for use in other keyboard models when the key arrangement is changed. Therefore, a simple and inexpensive scheme for keyboard control in a notebook computer, unencumbered by the existing limitations, is called for.